88 Sir John Robison on Cutting Curved-faced Files. 



Your Committee are quite satisfied that the plan proposed by Sir 

 John Robison is eligible, and that, when suitable tools have been pro- 

 vided for creasing them into their proper form, and the workmen have 

 had experience in using them, they will be able to produce half-round 

 files very superior to those cut in the usual way for certain kinds of 

 work. The smoothness of the cut will give the new files a decided pre- 

 ference. 



Your Committee beg to remark, that the file cut on the concave side 

 is the only one they have ever seen. As to making three-quarter round 

 or even cylindrical files on the principle suggested by Sir John Robison, 

 your Committee see no objection ; — difficulties may occur to the makers 

 in the first instance, but it is to be hoped these difficulties may be over- 

 come by experience. 



On the whole, your Committee conceive that Sir John Roblson's plan 

 of cutting and forming half-round and cylindric files with continuous 

 teeth, will be a decided improvement in a certain class of files, and that 

 the improvements are deserving of the marked approbation of the So- 

 ciety. James MijiNE, Convener. 



Edinburgh, 30fA January 1843. 



Extract from Letter Messrs Johnson, Cammell, & Co., Sheffield, to the 

 late Sir John Robison, K.H., F.R.S.E., February 13, 1843. 



The plan we have hitherto adopted in turning the half rounds, has 

 t)een by top and bottom hand-swages of block-tin, that is, by placing the 

 heated file on the bottom swage or groove, and turning it by hammering 

 the top swage or mandrel into the bottom groove. This was the simplest 

 method we could adopt to try the practicability of your communication ; 

 but we find it is not sufficiently powerful to effect and ensure in all cases 

 a regular curve, and which we suspect has, in a great measure, been the 

 cause of our failing in the hardening. 



We have now ordered tools, say swages, &c, of copper, to be "applied 

 under the screw-press, and by obtaining the curve the whole length of the 

 file gradually, and by one pressure, we hope will obviate our previous 

 difficulties ; and not leave those cranks or weak places, caused by the 

 hand-blow, and which in all cases shrunk or twisted in the hardening. 

 We expect in a few days to send you a few specimens from this process. 

 We have also considered your plan of turning by copper rolls, but fear, 

 from the causes herein named, it will not be very practicable. In all 

 cases of steel-rolling, the steel has a strong tendency to follow and curl 

 up after the rolls ; in ordinary cases of plain steel it can be easily reme- 

 died and straightened ; in this case the file would curl up after the rolls 

 on the convex side, and in adopting any plan to keep it straight from the 

 rolls, it would be liable to open out or disarrange the curvature of the 

 file and injure the teeth. Again, we suppose in rolling there would be a 

 danger of flattening or injuring the tooth of the file, unless the metal 

 forming the rolls was nearly as soft as the heated steel ; and if of the 



